1. Field of the Invention
This invention relates to a developing apparatus which can be used in an image forming apparatus such as an electrophotographic apparatus, and to a developer sealing member which can be used in the developing apparatus.
2. Related Background Art
An electrophotographic image forming apparatus, such as a printer, effects selective exposure on an image bearing body (photosensitive drum) uniformly charged by a charging device to thereby form a latent image, and visualizes the latent image with a developer (toner) by a developing device and transfers the image by the developer to a recording medium to thereby effect image recording. After the transfer, any developer remaining on the image bearing body is removed by a cleaning blade and the removed developer is stored in a cleaning container and the next development is effected by the image bearing body, the surface of which is clean.
In recent years, there has been put into practical use an apparatus in which the image bearing body, the charging device, the developing device, the cleaning portion, the waste toner box, etc. are collected into an integral structure and made into a cartridge, whereby a user loads the main body of the apparatus with the cartridge to enable the interchange of the parts of the developer image bearing body and thereby facilitate the maintenance thereof.
Further, when the life of the image bearing body extends and the number of printable sheets is increased, the developing device, which is otherwise limited in its supplying capability, is made into an independent unit. The apparatus is divided into the developing unit and a drum unit comprising the image bearing body, the charging device and the cleaning portion integral as image forming process means. Like the process cartridge, the mounting and maintenance of the main body of the apparatus are simplified, and the way of use conforming to the lives of the main parts has come to be adopted. In this drum unit, the waste toner produced by cleaning is stored in the cleaning container having a volume capable of being sufficiently contained in the life of the image bearing body, and is removed during the interchange of the drum unit.
In recent years, the demand for color electrophotographic image forming apparatuses capable of effecting the formation color images has been increasing. There is known, for example, a construction in which developing devices 105M, 105C, 105Y and 105K of four colors are all disposed in a rotary (for example, U.S. Pat. No. 4,707,108, U.S. Pat. No. 5,040,031, etc.).
Such a construction is very effective for forming colored images.
On the other hand, the future color electrophotographic image forming apparatus for copying with a network needs to cope with a large-quantity high-speed output irrespective of the propriety of the output of a color document. It is also desirable to reduce the cost per page to the level in a monochromatic electrophotograhic image forming apparatus.
To cope with such a desire, it is necessary to lengthen the lives of expendables used in this apparatus (such as the developing unit and the image bearing body unit which is the drum unit, or a process cartridge comprising the developing unit and the image bearing body unit constructed integrally with each other).
The developing unit is generally provided with developer sealing members on the opposite end portions of a developing roller.
The conventional developer sealing members, however, cannot sufficiently cope with the lengthening of the lives in some cases, and there has been a case where the developer (toner) leaks to the outside of the developer sealing members and contaminates the interior of the apparatus.
Also, in a situation in which the leakage of the developer occurs, the toner may adhere to a portion in which the developer sealing members are in close contact with a cylindrical member (such as the image bearing body or the developing roller (developing means)). Thus, there has arisen a case where the rotational torque of the cylindrical member becomes great and the load to the driving motor in the main body of the apparatus increases and stable operation cannot be accomplished.